Obviously it would be better if they're open source, since someone would be able to fix them, and it helps to know how your tools really work. But a better closed source driver is probably the right tool for most problems.
Merged into main still sounds like a gargantuan endeavor compared to opening a support ticket
So if you are a Linux user - simply avoid Nvidia. They don't care about you.
For workloads like training AI models, you would be shooting your business in the foot by using AMD.
It's only 15 years old!
If it takes them that long, it's very clear they don't care about Linux in general. Same thing is reflected in them not working with upstream kernel.
NVIDIA's drivers are practically the same size as an OS anyway. Arguably they are an OS, for the GPU instead of the CPU. So it's not a huge surprise they don't give it all away for free, especially as software is a competitive advantage for them.
Driver wise my worst experiences where all solidly in the ATI/AMD binary camp, with the constant need to exorcise nouveau from various systems second.